1. There are a few things that contribute to bad smells in milk. Although the cows diet can determine the taste of milk when it’s still good, when milk goes bad, the odor is due primarily to oxidation (by exposure to light and time), and bacterial development. Milk is a good solution for bacteria to grow in, and the bacteria that grow in milk produce a bitter and putrid flavor. Oxidation reactions in milk are catalyzed by light and copper. The compounds that produce the ‘cardboardy,’ ‘oily,’ ‘fishy,’ and ‘metallic’ flavors due to oxidation are primarily aldehydes and ketones. The aldehydes contribute more to the off-flavors than the ketones do. In addition to these compounds, propanal, pentanal, and hexanal also contribute to the flavors due to oxidation. The oxidation reactions that occur are the oxidation of the fatty acids present in milk. The fatty acids oxidize to form carbonyl compounds. The chain reaction on the separate page shows how the oxidation reaction proceeds. The combination of these bacteria and carbonyl groups that are produced in milk over time are what make milk smell so disgusting when it has been in the fridge past its expiration date.
Cited references: (1) Anderson, I.; Oeste, R. 1995. Sensory quality of UHT milk. Int. Dairy Fed. Spec. 9501 318-30. (2) Heath, Henry B. 1993. Flavors in Milk and Dairy Products. Dairy Ind. Int.; 48(9) 19-21. (3) Price, John C.; Manning, Donald J. 1983. The Flavor of Milk. Natl. Inst. Res. Dairy.;8(2) 50-1, 55-58. (4) Thomas, E.L. 1981 Trends in milk flavors. Journal of Dairy Science; 64(6) 1023-7. by Abigail Noble, 04'2. There are hundreds of chemicals in roasted coffee that are volatile. Of these, only some are aromatic. A list of the most potent of these chemicals provides twenty-three different chemicals. The most powerful of these aromatic chemicals are 4-vinylguaiacol, 4-ethylguaiacol, 4-hydroxy-2,5-dimethyl-3(2H)-furanone, and b-damascenone. These chemicals were discovered by an experimental procedure, which started with extracting ground coffee with a mixture of water, chloroform, and methanol. Then the same thing was done using just chloroform. The volatile components were then distilled off, leaving the nonvolatile parts, which cannot contribute to the aroma behind. Then, the resulting mixture was divided in half and one part was subject to dilutions, and the other to concentrations. After each dilution or concentration, the resulting mixture was tested for components by gas chromatography. These solutions were also checked using the human nose to aid in determining which compounds existed.
Structures of the most potent aromatic chemicals: 4-vinylguaiacol, 4-ethylguaiacol, 4-hydroxy-2,5-dimethyl-3(2H)-furanone, b-damascenone Cited reference: (1) Royal. Soc. Chem. (1996) 197, 200-205. by Adam Huron, 03'3. Methyl tert-butyl ether (MTBE) has been widely used over the past two decades as a fuel additive in commercial gasoline. It replaced lead as the primary oxygen- and octane-raising agent in gasoline because it was deemed to be more efficient and environmentally friendly. MTBE addition was also found to cause a significant reduction in the emission of greenhouse gases. However, recent investigation has concluded that MTBE is actually not environmentally friendly. Extensive studies have been undertaken on MTBE groundwater contamination and bacteriological degradation, in addition to controlled experiments on the effects of MTBE on mammals. Not only does MTBE persist in the environment, but it also can cause neurological damage to humans. Therefore, as part of recent legislation both within the United States and abroad, MTBE has been banned from widespread use. It is a major technological challenge for the petroleum industry to find a long-term replacement for MTBE.
Cited references: (1) by Adam Kern, 03'4. In general, flavors and smells are from low-molecular weight esters. An ester is made from a molecule of an acid uniting with a molecule of alcohol and then eliminating of a molecule of water. The following reaction shows a generic ester being formed. The ester that is commonly known as a major apple and strawberry flavor, for example, is (S) – 2 – methylbutanoic acid methyl ester. The characteristic fruit flavor is specific to the (S)-enantiomer. (S) – 2 – Methylbutanoic Acid Methyl Ester
Cited references: (1) Kwon, Dae Y.; Hong, Yun-Jeong; Yoon, Suk H. Enantiomeric Synthesis of (S) – 2 – Methylbutanioc Acid Methyl Ester, Apple Flavor, Using Lipases in Organic Solvent. J. Agric. Food Chem., 2000, 48, 524-530. by Aili Monahan, 02', Bryn Mawr5. Detergents and soaps improve the cleaning ability of water, working as surfactants and emulsifying agents between water and the oils in stains. They break up the oily binding between dirt particles and then help to rinse these particles away in water. Cleaning agents like detergent and soap are able to do this because of their amphipathic character, where each soap or detergent molecule has two very different ends: an ionic, hydrophilic head group, and a long, nonpolar, hydrophobic hydrocarbon tail. The polar head group will easily dissolve in water, while the nonpolar tail will avoid water and be attracted to grease, making it possible for detergents and soaps to dissolve in both water and oil. Many tails will attach to a particle of grease in a stain and surround it, forming a spherical cluster called a micelle, with the grease and tails on the inside and the polar heads on the outside. The heads bond with water (through hydrogen-bonding), making the droplet now soluble in water, so that it can be rinsed away, removing the stain. Detergents and soaps are emulsifiers that bridge the oil-water line and cause droplets of oil to become dispersed into water, although the two liquids are normally insoluble in each other. (This process of dispersing immiscible liquids into each other is called emulsion, and it is only stable when an emulsifier is used.) Since they affect the interface between oil and water, soaps and detergents are also examples of surfactants (surface active agents). They reduce surface tension between the two phases, increasing contact and wettability, and helping emulsion. Detergents and soaps also have alkaline “builders,” like sodium carbonate, for example, which bind to dissolved metal ions and help emulsification. Although detergents and soaps work in much the same way, there is a disadvantage to traditional soap when it’s used in water that contains metal ions (hard water). The sodium carboxylates in soap can become insoluble calcium and magnesium salts, causing “soap scum” deposits when the water dries. Synthetic detergents do not do this because they do not have sodium carboxylates. Here are examples of soap and detergent molecules: Soap: Synthetic Detergent: Detergents and soaps may also contain bleach, which alters the stain molecules’ structure or bonding so that they reflect white light, or brighteners, which work through fluorescent action, absorbing ultraviolet light and then reflecting blue light (making up for the yellowish tint of aging fabric). They may also use enzymes to cleave protein or fat molecules in food stains, helping emulsification. In general, the great cleaning powers of soaps and detergents come from their amphipathic characteristics and action as emulsifiers and surfactants, able to dissolve in both oil and water.
Cited references: (1) Bloomfield, Louis A. “Cleaning Agents.” Scientific American 282 (April 2000): 88-89. (2) McMurry, John. Organic Chemistry. New York: Brooks/Cole, 2000. 1122-1124. by Carrie Black, 03'6. THC (more specifically delta – 9- THC) binds to the CB1 cannabinoid receptor, which is expressed on many cell surfaces in humans, including neuronal and brain cells. Under most conditions the CB1 receptor, when it interacts with a cannabinoid, for example THC, can inhibit cell signal transduction that relies on adenylate cyclase and cAMP, a common second messenger used for cell signaling. They probably do this using a G-protein, another type of second messenger. The inhibition of N and Q type calcium channels results, which could explain the psychological effects of marijuana: the inhibition of N channels decreases neurotransmitter release in many parts of the brain. It turns out that CB1 is localized to regions of the brain that are affected by N channel inhibition and also which are responsible for control over the functions that marijuana alters (i.e. the effect of CB1 –THC binding as well as the location of such receptors offers an explanation for the effects of marijuana): the hippocampus (memory), cortex(perception) and cerebellum(coordination), as well as along many sympathetic nerve terminals. THC – CB1 binding can also activate certain MAP kinases through a G-protein, which are responsible for the expression of certain proteins, presumably responsible for the effects of marijuana. Finally, there is evidence that suggests that cannabinoids can have the receptor-independent effect of mobilizing components of an endogenous cannabinoid, anandamide, which bonds to CB1 and probably other undiscovered cannabinoid receptors. Thus THC produces at least some of its effects by affecting the function of cell signaling pathways, resulting in varied consequences.
Cited references: (1) Felder, Christian C; Glass, Michelle. Cannabinoid Receptors and their Endogenous Agonists. Annual Review of Pharmacology and Toxicology (1998), 38, 179-200. (2) Gatley, J; Lan, R; Volkow, N; Pappas, N; King, P; Wong, C; Gifford, A; Pyatt, D; Dewey, S; Makritannis, A. Imaging the Brain Marijuana Receptor: Development of a Radioligand that Binds to Cannabinoid CB1 Receptors in Vivo. Journal of Neurochemistry (1998), 70(1), 417-423. (3) Matthew, R; Wilson, W; Turkington, T; Coleman, E. Cerebellar Activity and Disturbed Time Sense after THC. Brain Research (1998), 797, 183-189. by Chris Bennett, 03'7. Hemoglobin in the red blood cell is composed of four subunits, two a and two b. Each subunit contains one heme prosthetic group. In the center of the heme is an iron atom that is normally in the ferrous, Fe2+, oxidation state. The iron atom is coordinately bound to four nitrogens on the same plane. In the fifth coordinate, perpendicular to the plane of the nitrogens, the iron atom is bound to His F8. It is in the sixth coordinate where oxygen is bound. And since each hemoglobin has four subunits, and within each unit there is a heme group, one hemoglobin can carry up to 4 oxygen molecules. The binding of oxygen to the hemoglobin is both reversible and cooperative. It is reversible because hemoglobin will exchange oxygen for carbon dioxide in the lung and vice versa near the cell. The cooperative property of hemoglobin reveals that one binding of oxygen to one of its heme group will increase the affinity for oxygen binding to the next group, and so on. The transfer of oxygen is regulated by pH and concentration gradient, as the lung is rich in oxygen while cell are polluted with carbon dioxide. Other molecules, such as 2,3-BPG, also play important role in the binding/releasing of oxygen..
Cited references: (1) by Chung Nguyen, 03'8. When tested among twenty-five NCAA Division 1A football players from a university in the mid-south region of the US who were subjected to random drug testing and forbidden to take any other types of anabolic or androgenic steroids or any other nutritional supplements during the testing, it was found that 28 days of creating supplementation during strength and agility training during the off season from football promoted gains in fat- and bone-free mass, isotonic lifting volume and sprint performance when compared with subjects who took merely a placebo of mostly glucose. Further, when tested among twenty-three healthy males in another study of the same structure and intent who all had at least one year of weight lifting experience and lifted weights 2-3 times per week, the results illustrated were fairly dramatic in favor of strength gain when diet is supplemented with creatine monohydrate. Arm flexor strength (without standard deviations, as you can see those in the article) increased in the placebo group from 42.5 kg to 49.3 kg in a 6-week period (rather than a four week period as in the previous study) and in the creatine group increased from 42.8 to 54.7 kg. There was subsequently a 29.9% increase in strength of those who took creatine and a 16.5% increase in those who took the placebo. Consequently the results show that creatine monohydrate as a dietary supplement, when taken in conjunction with regular resistance and agility training is shown to produce increased lean mass as well as greater strength gains and a greater ability to produce ATP, thus improving repetitive sprint performance capacity. Because the presence of phosphocreatine stored in muscles is largely the cause of energy used to rephosphorylate adenosine diphosphate (ADP) to adenosine triphosphate (ATP), taking creatine was also shown to increase the muscles ability to carry out this process, improving overall short-burst performance. Chemical Structure of Creatine:
Cited references: (1) “Effects of oral creatine supplementation on muscular strength and body composition” by M. Daniel Becque et al. Medicine and Science in Sports and Exercise (1998) 30, pages 73-82. (2) “Effects of creatine supplementation on body composition, strength, and sprint performance” by Richard B. Kreider et al. Medicine and Science in Sports and Exercise (2000) 32(3), 654-8. by Dan Mone, 03'8. Any ideal adhesives must exhibit a few basic properties: it must be able to be stored in a relatively inactive state; it must quickly and efficiently form a cohesive and adhesive bonding network, and this formation of bonds must be triggered by an outside stimulus. Ethyl cyanoacrylate, the active compound in superglue, exhibits all of these attributes. The term “ethyl cyanoacrylate” or “ethyl cyanoacrylate ester” refers to one of many compounds in the cyanoacrylate family. Others include methyl, allyl, and ethoxymethyl cyanoacrylate esters. The diversity in this family of compounds lies in the fact that much research and innovation has been carried out to increase the performance, temperature resistance, and durability of common household superglue for more rigorous uses - namely for use as an industrial adhesive. As a result of recent studies, many such variants of this compound have been tested and developed, but they all fundamentally behave the same way. Superglue joins two surfaces by anionic polymerization. “Ethyl cyanoacrylate” actually refers to the monomer in such a construction. In a slightly acidic solution, the molecules remain un-reactive, suspended in their monomer form. Upon the introduction of a weak base to the system (OH- from H2O works perfectly and is found on virtually any surface), OH- ions bind to the positive dipole of the molecule and sets off an exothermic chain reaction in which the cyanoacrylate monomers form a linear chain. (The positive dipole binds to an induced negative site on another molecule, etc..) In the presence of an acid, (superglue is stored in a slightly acidic medium) the partially negative site is bound by the acid molecule, blocking polymerization. The effect of acids and bases on cyanoacrylate polymerization has been implemented in the production of some new products. Preparation sprays, which often contain bases and/or tertiary amines, are used to accelerate the bonding process. Like bases, amines contain a lone electron pair that can easily bind to the positive dipole on the cyanoacrylate monomer and initiate polymerization. After a surface has been prepared, the “cure time” (the time fore the adhesive to set) often reduces to just a few seconds. Ultimately, the scientific journals consulted were not the most pertinent resource for learning the chemical behavior of superglue. This is primarily due to the fact that the chemistry of ethyl cyanoacrylate has been known for many years. Current studies do not focus on the relatively simple mechanism of the adhesive, but rather employ it to study more complex polymerization and photopolymerization reactions. A study by Viktor V. Jarikov and Douglas C. Neckers explores the process of using photopolymerization to induce the anionic polymerization in methyl cyanoacrylate. In this experiment, scientists mixed inert compounds “(crystal violet) leuconitrile” and “(malachite green) leucohydroxide” with methyl cyanoacrylate. Although these two compounds remained generally un-reactive to the adhesive, photo induced lyses of these molecules produced anions which did react with the adhesive. In this way, scientists could incite polymerization simply by introducing ultraviolet light into the system. Because the photogenerated anions and cations displayed bright colors, the process of indirect polymerization could be monitored step-by-step. Ethyl cyanoacrylate, like it’s similar counterparts, is one of the few synthesized compounds that undergo polymerization without the need of a catalyst. All that is required is a few molecules of H2O, which are found on almost any surface or floating around in the gas phase. Even a miniscule amount of base sets off a chain reaction which induces massive polymerization. Long chains of cyanoacrylate monomers extend into the pores and crevices of each surface, forming root-like projections that anchor the two surfaces together. To balance high reactivity, acid and base chemistry has been implemented to develop means of controlling the polymerization more readily. Because of the extensive research being carried out to make this class of adhesives more efficient for industrial use, we are gaining useful knowledge about polymers in general as well as ways to direct their behavior.
Cited references: (1) Courtney, Patrick J. and Verosky, Christopher. “Advances in Cyanoacrylate Technology for Device Assembly.” Medical Device & Diagnostic Industry Magazine. Sept. 1999 ed.9. Rubber (and synthetics) are composed of a number of individual chains that all have some elastic properties as well as elastic interactions between the strands. Each of these strands is believed to consist of a number of rigid links between chemical crosslinks that allow them to flex in relation to one another. These polymer chains do not come together in a particularly well-organized structure. Instead, they often come together in structures that contain defects like free ends and loops in the chains and interact in such a way as to stretch when they are pulled, but not to separate from each other and the structure as a whole.
Cited references: (1) Arruda, Ellen M.; Przybylo, Phillip A. “An investigation into the three-dimensional stress-birefringence-strain relationship in elastomers.” Polymer Engineering and Science (1995) 35:5, 395-398. by Emily Christiansen, 03'10. Although behavioral tendencies are not fully understood, testosterone can be linked to aggressive behavior in naïve male quails through a mechanism devised by Schlinger and Callard. The importance of testosterone in aggression was shown in earlier studies where an absence of circulating testosterone decreased aggressive behaviors significantly. Schlinger and Callard believe testosterone is converted into estradiol-17B (E) and 5a-dihydrotestosterone (DHT), biologically active metabolites, by aromatase and 5a-reductase. E binds to its receptors and increases stimulation of aromatase. Testosterone and DHT contribute by increasing formation of estrogen receptors, believed to be involved in neural activation. Aromatase activity is highest in the areas of the brain most closely associated with aggressiveness, such as the preoptic area. They believe that aggression may be activated by aromitization of testosterone in the central nervous system. Although the study’s results are exclusive only to naïve male quails, due to the similarities of hormonal systems across species, it is a mechanism that is most likely very similar to those of other animals, including humans.
Cited references: (1) Schlinger, BarneyA; Callard, Gloria V. "Aggressive behavior in birds: an experimental model for studies of brain-steroid interactions." Biochem. Physiol. A: Comp. Physiol. 1990, 97A(3), 307-316. by Eric Adiarte, 03'11. At puberty, people develop apocrine glands that secrete odorless sweat onto the skin in certain places such as the armpits. Microorganisms find the warm, moist skin near these glands an ideal environment, and they emit the smell that we know as body odor. Deodorants are designed to control body odor. They do so both by controlling the skin bacteria population and by masking body odor. Triclosan, or 2,4,4-trichloro-2-hydroxydiphenyl ether, is a commonly used deodorant. It prevents the bacteria on the skin from growing or reproducing. Antiperspirants, which are designed to reduce the volume of sweat, tend to use non-organic active ingredients, particularly aluminum and zirconium.
Cited references: (1) Schamper, T. Journal of Chemical Education (1993) 70, 242-244. by Esther Glick, 03'12. There are many structures that are involved in creating sweet smelling fragrances. One of those structures is 5-methyl-2-(2’-oxo-3’-butyl)phenol. “This novel compound of 5-methyl-2-(2’-oxo-3’-butyl)phenol emits a characteristic sweet fragrance and a perfume composition comprising this compound is also provided*.” Another organic structure that is involved in the making of sweet smelling fragrances is the carbonyl group. On May 18, 2000, there was a patent put out on an invention that relates carbonyl compounds to fragrances. “The invention relates to carbonyl compounds of the general structure (I) where the rest R1 is hydrogen or an akyl group with between 1 and 5 carbon atoms, the rest R2 and R3 independently of each other are hydrogen or an akyl group with between 1 and 3 carbon atoms and one of the positions C-1/C-2, C-2/C-3 or C-1/C-6 has a C=C double bond, and the rest R4 is either hydrogen or, if the C=C double bond is situated in C-2/C-3, hydrogen or an akyl group with between 1 and 3 carbon atoms . The below compounds are characterized by interesting fragrance notes of great intensity and are suitable for use as fragrances in, for example, cosmetic preparations, technical products or perfumed spirits**.”
Cited references: (1)*http://l2.espacenet.com/dips/abstract?CY=ep&LG=en&PNP=US4428868&PN=EP0058906&CURDRAW=0&DB=EPD&ABSFLG =%05&DRDB=US1 Patent Number: US4428868 Publication Date: 1984-01-31 Inventor(s): Takahashi Katsuhiro (JP); Yoshida Toshio (JP) (2)**http://l2.espacenet.com/dips/abstract?CY=ep&LG=en&PNP=DE19851684&PN=DE19851684&CURDRAW=0&DB= EPD&ABSFLG=%05&DRDB=DE1 Patent Number: DE19851684 Publication Date: 2000-05-11 Inventor(s): Lemke Ute (DE); Veit Elke (DE); Markert Thomas (DE); Nemitz Ralph (DE); Porrmann Volker (DE); Speitkamp Marc (DE); Ten Pierik Theo (NL) by Gary Tong, 03'13. A sunburn results when the skin is overexposed to the ultraviolet rays of the sun. The outer layer of the skin (epidermis) produces melatonin, which gives the skin its color, in an attempt to protect underlying tissue from the harmful effects of the sun’s rays. Exposure to ultraviolet radiation stimulates the melanocytes to produce tiny granules of melanin, which migrate into neighboring cells called keratinocytes. As old skin dies and new cells grow in from below, the newly pigmented keratinocytes work their way over 4 to 5 days to the topmost layer of skin. There they produce the color craved by sun worshippers. Melanin, the modified protein than darkens skin, can block some of the harmful effects of ultraviolet radiation.
Cited references: (1) Corinna Wu "Unraveling the Mystery of Melanin" Science News (1999) 156, 190. (2) www.health-center.com|Wellness-skin/Dermatology (3) Berkow, Robert, MD, ed. The Merck Manual of Medical Information, home edition. Merck & Co., Inc. WestPoinnt, PA (1997). (4) Larson, David E., MD, ed. Mayo Clinic Family Health Book, second edition. William morrow and Company, Inc. New York (1996). by HeMin Kim, 03'14. All of us at some point in our lives have had close encounters with cockroaches - and rewarded them with a nasty shower of harmful chemicals from a Raid, Black Flag, or Combat aerosol can. The ingredients of these insecticides include many different organophosphorus (OP) chemicals, such as chlorpyrifos and diazinon, as well as synthetic pyrethroids such as permethrin (Ludvik). These chemicals kill insects by entering their respiratory system and strongly exciting their nervous systems into hypersensitivity – leading the supercharged nerves to paralysis and death. However, use of bug spray must be used carefully, since documented harmful affects have been found for human beings. OP chemicals (which are electrophilic compounds!) attach to a certain enzyme (AchE) found in the nervous system of vertebrates, and phosphorylize it, rendering it inactive. AchE then accumulates in excess in the synapses of the parasympathetic nervous system, leading to uncontrolled impulses. Symptoms for human beings include restlessness, lethargy, mental confusion, loss of memory, and deficits in neurophysiological functions. Insecticides have also been thought to be a factor in Non-Hodgkin’s lymphoma, leukemia, and lung cancer (Mileson). However, these findings remain inconclusive, since the people studied had excessively high dosages of the insecticide, and methods for assessing the exposure of multiple chemicals through routes and times of exposure (low dose/high dose) were not well documented. Therefore there is no real evidence that normal household use of bug spray is significantly harmful for a person. However, the backside of a Raid can stresses that if the chemical comes in contact with human skin, it should be immediately washed off, and that the location where it sprayed should be fully ventilated to avoid unnecessary inhalation of the chemicals. Noting the above said, caution must be exercised and one should think twice before reaching for a spray can – and perhaps – is better off by reaching for a shoe instead. Chemical Structures
Cited references: (1) Ludvik, George F.“Insecticide”. [Online] 29 October 2000.15. With regard to Chinese Restaurant Syndrome (an illness affecting some people who ingest Chinese foods, then experience flushing, tightness in the chest, difficulty in breathing, etc), there has been no evidence citing Monosodium Glutamate as the cause. Testing in a controlled environment of people susceptible to the so called illness found MSG did not cause any syndromes, even in asthmatics. In small doses, such as those in ethnic foods, MSG has been found harmless. Even in excessively large doses of 150 mg/kg body weight, humans have been found to be able to metabolize MSG without trouble, both as adults and infants.
Cited references: (1) Walker, R. “The Significance of Excursions above the ADI: Case Study: Monosodium Glutamate,” Regul Toxicol Pharmicol, Oct 10, 1999, p. S119-121. by Jeff Barton, 04'16. Amanita Phalloides releases the bicyclic peptide Phalloidin (also known as Phallocidin). This organic substance interferes with cell function and motility in many cell lines, inducing poisoning, and in some in vivo cases, death. The specific mechanism of Phalloidin is in its binding to the omnipresent cytoskeletal protein, actin. It interferes with the de-polymerization of F-Actin and, when G-Actin polymerizes, it interferes with either the reversal of that, or the effects of an actively depolymerizing cytotoxin such as Cytochalaisin B. By interacting with actin, it interferes with all functions associated with the actin cytoskeleton, including but not limited to liver, kidney, and muscle function.
Cited references: (1) Proc Natl Acad Sci U S A (1974) 71(7), 2803-7. Related Articles, Books Interaction of phalloidin with actin. Lengsfeld AM, Low I, Wieland T, Dancker P, Hasselbach W PMID: 4368830, UI: 74302961 (2) FEBS Lett 1975 Jun 1;54(1):73-5 Related Articles, Books Spectroscopic evidence for the interaction of phalloidin with actin. Wieland T, de Vries JX, Schafer A, Faulstich H PMID: 1132496, UI: 75168211 (3) FEBS Lett 1975 Jun 15;54(2):263-5 Related Articles, Books Stabilization of F-actin by phalloidin. Reversal of the destabilizing effect of cytochalasin B. Low I, Dancker P, Wieland Th PMID: 124264, UI: 75168252 (4) FEBS Lett 1974 Sept 46(1)351-3 Phallotoxins Bind to Actins. Wieland Th and Govindan V. by Jeremy Pober, 03'17. When cultivating various plants and flowers the result uses the colors displays from other species. This changing of chemical makeup is what can verify the various colors that spur from the same plants. For example, the carnation that is a flower of many colors, in one circumstance exists in a pink form. When the flowers share a “basic magenta hue” they are called cyclamen or fuchsia. The assessment of the codes that produce the variations is through the use of a colorimeter. The pink shade of the carnation is based on a disubstituted B ring anthocyanin. For the red-mauve coloration in carnations the substitution cyaniding 3,5 di-o-glucoside is responsible. In the pink, however, the pelargonidin 3,5-di-O- - glucoside (6’’, 6’”-malyl diester) is responsible for the given hue. The pelargonidin is the major anthocyanin present which is not a very stable molecule because of the weak bridging malyl group that readily breaks with sugars in acidic mediums. This presence of the new macrocyclic anthocyanin is what makes pink carnations.
Cited references: (1) J. Agric. Food Chem.,(2000) 48, 22-26. by Jessie Wieland, 03'18. Funnel-web spiders’ venoms are lethal in that the venom blocks ion receptors and receptors necessary for balance within the organism. In 1993, scientists extracted venom from a funnel-web spider and studied it. This compound was named “HF-7”. HF-7 is a polar compound which blocks the kainite receptors that are crucial for maintaining proper functional properties of nerve cells. Scientists used several methods of analyzing this unknown venom. Through ultraviolet absorption spectroscopy, they found that this venom had guanine chromophore. Also, through fast action bombardment (FAB) technique, scientists found the exact molecular formula. The molecular formula was C12H24N5O16S2. This particular venom was interesting to scientists because HF-7 was one of two naturally occurring sulfated nucleosides. Scientists tried to use NMR spectroscopy to observe H-C multiple bonds, but there was a limited amount of natural HF-7 available How this HF-7 becomes lethal models after most receptor and ion channel inhibitor cases. This toxin blocked kainite receptors related with neurons and L-type calcium channels. Blocking of the calcium channels thwarts the body from responding to excess carbon monoxide levels. Also, blocking the kainite receptors an lead to cardiac arrest. Blocking of the calcium levels prevents passage of neuro-transmitted signals to pass from one neuron to another neuron.
Cited references: (1) by Joe Kim, 02'19. An easy response to this question is to say “the ingredients”. To avoid such an answer, my research became focussed on which ingredients increased or decreased the SPF value (what high SPF sunscreens contain). The most common ingredients between references and abstracts were Para Amino Benzoic Acid (PABA, picture attached) and its derivatives, salicycites and anthranilates. There were not, however, any articles explaining why these ingredients provided protection against the sun, which is what I had hoped to find. To my knowledge, this has something to do with the absorbance by the ingredients of the light frequencies that damage the cells in the skin. The ingredients do this to stabilise their structures by resonance. The article that I am turning in, Comparative skin irritations of high and low SPF sunscreen products, shows that in fact there is no correlation between the SPF rating and skin irritation. Furthermore, SPF ratings vary between companies, and actually prove to be quite an abstract value given by companies. This is partly due to the many methods of evaluating a sunscreen’s protection, and also the thickness of the layer applied to the skin. The article proves this by evaluating many sunscreens on many patients with different spectroscopic methods.
Cited references: (1) FIX Comparative skin irritations of high and low SPF sunscreen products Silber, Paul M.; Mills, Otto H. Jr.; Drammers, Folk, Charles M.; Gaust, Richard, F; Stephen, Thomas J. (1990) by Marcel Dekker, Inc. by Jonathan Hull, 04'20. Fundamentally, the purple coloration of eggplant skin is due to the presence of flavanoids, "one of a group of naturally occurring phenolic compounds many of which are plant pigments" (w1.xrefer.com, 2000). The specific type of flavanoid found in eggplant skin is anthocyanin, a pigment which occurs "in the cell vacuoles of various plant organs and [is] responsible for many of the blue, red, and purple colors in plants (particularly in flowers" (w1.xrefer.com, 2000). Moreover, through a series of experiments, Satanura, Watanabe and Obata isolated and discovered the structure o fthe major anthocyanin in eggplant, nasunin, to be: delphinidin-3-(p-coumaryl-L-rhamnosyl-D-glucoside)-5-glucoside chloride (I) (Satanura, Watanabe & Obata, 1963). In an experiment by Shingawa et. al. concerning the change in anthocyanin pigments over time, Shingawa and his colleagues found this major eggplant anthocyanin, nasunin, to be particularly stable (Shingawa, 1997). The reason that the presence of this organic molecule causes the eggplant to appear purple is that anthocyanins have extended systems of conjugation. Thus, their absorbtion spectra extend from the UV all the way into the visible region (McMurry, 2000). Anthocyanins must have an absorption in the yellow wavelength region of the visible spectrum, so that we see white light with the yellow removed which we percieve as purple.
Cited references: (1) http://w1.xrefer.com/entry/485457 (11/19/00). (2) McMurry, John. "Conjugated Dienes and Ultraviolet Spectroscopy." Organic Chemistry, 5th ed.; Brooks/Cole: New York, 2000; 547-548. (3) Sakanura, S.; Watanabe, S.; Obata, Y. "The Structure of Anthocyanin in Eggplant." J. Agric. Biol. Chem. (1963) 27, 663-665. (4) Shinagawa, Hiroko, et. al. "Change in Anthocyanin Pigments during the Maturation of "Shibazuke" Japanese Pickels." Nippon Kasei Gakkaishi. (1997) 48, 1071-1076. by Catherine O'Conor, 03'21. Many people believe that the changing colors of leaves on deciduous trees in autumn is tied to the cooling temperatures. Although the cooling temperatures of fall have an effect on the intensity of the colors we see in the leaves, the real reason the brilliant colors of fall emerge is the shortening period of daylight (or photoperiod) that begins to decrease in late summer. As the length of daylight decreases, the chlorophyll contained in the leaves of the plants breaks down, because a layer forms in the petiole, or leaf stalk, of the leaves, which stops the supply of phosphorus and magnesium to the chloroplasts. The chlorophyll thus wears out and is not replaced, as it normally is during the rest of the year. Chlorophyll works to get the plant food by absorbing light from the sun and using it to energize the process of photosynthesis. The structure of chlorophyll is such that, owing to the number of conjugated bonds, it reflects green light and absorbs all other frequencies of light, especially blue and orange light. However, not all green light is reflected. Carotenoids and xanthophyll are two pigments that absorb frequencies of light that chlorophyll cannot, thus making the absorption of light more thorough and efficient. Both substances can transfer the light energy they capture to chlorophyll, and photosynthesis can be energized. Carotenoids give orange pigments, such as in carrots, and xanthophyll gives yellow pigments. These substances are in the leaf at all times of the year, but can only be seen when chlorophyll breaks down in the fall and is absorbed into the leaf stem. Thus, the yellows and oranges are revealed and we see beautifully colored leaves. There is another pigment that results in the purples and reds that we also see in autumn leaves. It is called anthocyanin and is favored when temperatures are lower, or if there is not very much rain in early fall. Anthocyanin is produced in the sap of the leaf cells. Drought conditions favor anthocyanin production because the soil water deficiency effects the plant’s metabolism, and also nitrate absorption by the leaf is reduced. The combination of these factors causes picturesque fall time displays.
Cited references: (1) Munné-Bosch, S, Alegre, L "Changes in carotenoids, tocopherols and diterpenes during drought and recovery, and the biological significance of chlorophyll loss in Rosmarinus officinalis plants." (1999) Planta 210: 925-931. (2) Demmig-Adams B, Adams III WW, Verhoeven, AS "The xanthophyll cycle and acclimation of Pinus ponderosa and Malva neglecta to winter stress." Oecologia (1998) 118: 277-287. (3) websites: http://www.esf.edu/pubprog/brochure/leaves/leaves.htm; http://www.sciam.com/askexpert/environment/environment18.html; http://www.nps.gov/blri/flowers.html; http://www.ces.ncsu.edu/nreos/forest/topics/leafco~1.html. by Katie Unger, 03'22. Tree sap is sticky because it contains large amounts of sucrose and water. Since sucrose has many hydroxyl groups, it can participate in dipole-dipole and hydrogen bonding interactions with many different water molecules. This creates large sucrose-water systems. Immediately surrounding the sucrose molecules are hydration layers of highly compressed water molecules, and as the water molecules get farther away from the sucrose, they act more and more like pure water. The equatorial hydroxyl groups on sucrose allow water molecules to pack well around the molecule. There is a lot of physics and physical chemistry (way over my head) involved in making this sticky, but in general it is enough to say that sap is sticky because of the close-packed interaction between sucrose sugars and water molecules. Chemical Structure of Sucrose:
Cited references: (1) Sneha A. Parke and Gordon G. Birch; Solution Properties and Sweetness Response of Selected Bulk and Intense Sweeteners, Journal of Agricultural and Food Chemistry; 1999; 47(4); 1378-1384. (available at http://pubs.acs.org/isubscribe/journals/jafcau/jtext.cgi?jafcau/47/4/html/jf9807521.html) by Kevin Jones, 03'23. Phosphocreatine is produced naturally in the liver and kidneys and is found in high concentrations in muscles that have high-energy demands, namely, skeletal muscle. Additional creatine can also be ingested in red meat, which has a concentration of approximately 4g per kg. (Sahelian) Phosphocreatine (PCr), along with creatine kinases (CK), facilitates the production of ATP from ADP during muscle contraction (Korman). A buildup of ADP in the muscle causes acidification (lactic acid buildup), which contributes to the soreness often felt after extreme muscle activity. By increasing PCr levels in the muscle tissue, ADP can be rapidly re-phosphorylated to form ATP by the following reaction: (Korman) The rate at which this reaction proceeds is much faster than the rate at which ATP can be broken down. As long as PCr is present it supplies the muscle tissue with ATP. In order to boost the level of PCr in the muscles an oral supplement can be ingested in the form of creatine monohydrate (Vandenberghe). An additional 4g of creatine monohydrate per day enables the user to complete more intensive and longer workouts as well as increase maximum output of their muscles. Dosages of over 4 g have shown no advantage and may place unnecessary strain on the kidneys (Kreider). Since the normal amount of ATP found in muscle tissue is usually exhausted in 10-15 seconds of exertion, this dosage of creatine gives the muscles an increased energy reserve (Kreider). Studies have shown that creatine supplementation does not have an appreciable effect during endurance workouts. This is most likely because the energy for endurance activity is obtained from glycogen stores, not ATP stored in muscle tissue. Creatine supplements do not, by themselves, build muscle. Increased muscle mass is gained only by combining muscle activity with creatine’s use to take advantage of the extra energy. Among weightlifters, users are enabled to increase repetitions with more weight. This enhanced workout is what builds muscle tissue. (Terjung) Structure of Creatine Monohydrate:
Cited references: (1) Sahelian, Ray. “Creatine – just the FAQs, ma’am.” Better Nutrition (2000) 62.5: 26. (2) Kreider, R.B. “Effects of creatine supplementation on body composition, strength, and sprint performance.” Med. Sci. Sports Exercise (1998) 31.1: 73-82. (3) Korman, Ben. “Phosphocreatine Circuit System and Benzaldehyde Derivatives.” Heidelberg College (1999) http://www.heidelberg.edu/depts/chm/creatine.html. (4) Terjung, Ronald L. “The physiological and health effects of oral creatine supplementation.” Medicine and Science in Sports and Exercise (2000) 32.3: 706-17. (5) Vandenberghe, Kathleen and Paul Van Hecke, Marc Van Leemputte, Florent Vanstapel, Peter Hespel. “Phosphocreatine resynthesis is not affected by creatine loading.” Medicine and Science in Sports and Exercise (1999) 31.2: 236-42. by Kevin Meyers, 03'24. Many organic acids are already present in apples, including malic acid and citric acid. The article I found details an experiment exploring the effects of many kinds of browning inhibitors, including calcium/ organic acid salts and SH- compounds. The experiment showed that when in mixtures of various chemicals, the inhibitors were able to both conserve the malic acid present in the apples, as well as to inhibit the browning process. It is stated in this article, though it was not part of this experiment, that n-ascorbic acid and isoascorbic acid have equal effect on browning. The experiment shows that those compounds with a higher concentration of isoascorbic acid have less tendency to brown during storage, though with less effect than the presence of the SH- compounds. In short, this experiment does not show the effects of ascorbic acid alone, but as part of a mixture of antibrowning compounds. However, it is clear that the ascorbic acid helps retain the natural acids in the apples, including malic acid, citric acid, and quinic acid.
Cited references: (1) Buta, J. George; Moline, Harold E.; Spaulding, David W.; Wang, Chien Y.. “Extending Storage Life of Fresh-Cut Apples Using Natural Products and their Derivatives.” Journal of Agricultural and Food Chemistry. (1999) Vol 47, No 1. (2) “Food additive” Encyclopædia Britannica Online. (1994-2000)25. I couldn’t find any studies that dealt directly with the mechanism of rBGH. Most of the studies investigated the optimal amount to administer, or the DNA structure of the molecule. The articles I requested over ILL did contain some interesting information, even though they didn’t really answer my question. The authors suggest some ideas for why rBGH increases milk production such as its diabetogenic and lipolytic activity. This activity suggests that the hormone “mobilizes body fat and diverts glucose and fatty acids from tissue deposition to increased milk production” (Hart, Bines et al). They suspect that something else is involved such as growth hormone (GH) stimulating the synthetic capacity of the mammary gland. In studies attempting to figure out the mechanism of milk increase, it was noted that goats treated with GH showed an increase in blood flow in mammary tissue. One of the side effects of rBGH is that milk fat can increase and protein can decrease. This hasn’t been shown in all studies, and it is believed that these changes depend on the cow’s energy status and nitrogen balance. If the cows are in negative energy (losing weight) and nitrogen balance, they tend to have higher fat and lower protein milk. Researchers have also noted a lag time for rBGH to take effect (around a week) and another lag time for milk production to return to normal. This effect depends on the cow’s stage of lactation. While none of this really answers my question, it’s interesting to think about, and probably related to the way in which rBGH raises milk production.
Cited references: (1) Enright, W.J., Chapin, L.T., Moseley, W.M., and Tucker, A. “The Effects if Infusions of Various Doses of Bovine Growth Hormone- Releasing Factor on Growth Hormone and Lactation in Holstein Cows. “ J. Dairy Sci. (1988) 71:99-108. (2) Hart, I.C., Bines, J.A., James, S., and Morant, S.V. “The Effect of Injecting or infusing Low doses of bovine growth hormone on milk yield, milk composition and the quantity of hormone in the milk serum of cows.” Anim. Prod. (1985) 40:243-250. by Liz Hunt, 03'26. Soda bottles are waterproof due to the kind of plastic they are made out of. Most soda bottles, such as those used by major soft drink companies such as Coke and Pepsi, are made out of the plastic polyethylene terephthalate, or PET for short. PET is a hydrophobic plastic, which used not only in soda bottles however it is also used in clothing as well as a polyester fabric. PET is hydrophobic because it has such a high water contact angle. The water contact angle of a substance is the “angle formed between the surface of a solid and the line tangent to the droplet radius from the point of contact with the solid.” (http://www.osmotics.com/products/Page772.htm) When the water contact angle becomes high enough, the liquid tends to bead away from the solid, which is what we see in our soda bottles. This can be attributed in part to the surface tension and rigidity of the PET molecule, which in turn, can be attributed to the structure of the PET molecule. The PET molecule would be a rather flippant structure, except for the benzene ring in the middle of the PET structure, which adds rigidity to the molecule. Not only is this rigidity in the molecule the cause of our soda bottles being waterproof and strong, it also allows the PET, when used as fabric in clothing, crease – resistant.
Cited references: (1) Addition of Glycolic Acid to Polyethylene Terephthalate (PET). http://www.chem.mtu.chemistry/PAGES/CHLEC/CH462/aaronandjessica/HomePage.html (11/4/00). (2) "Polymer of the Day: POLYETHYLENE TEREPHTHALATE (PET)" http://arvind.coe.drexel.edu/MATE200/PET.html (11/5/00) (3) Drelich, J.; Payne, T.; Kim, J. H; Miller, J. D.; et al. Selective froth flotation of PVC from PVC/PET mixtures for the plastics recycling industry. Polm. Eng. Sci. [Online] 1998, 38(9), 1378 – 1386. (4) Rudie, Brian. Hydrophilicity and Hydrophobicity. http://www.osmonics.com/products/page772.htm (11/5/00) by Logan Dempsey, 03'27. Sarin functions by breaking down the enzyme acetylcholinesterase that is responsible for breaking down the neuromuscular transmitter acetylcholine. Acetylcholine carries the signals between the nerves and muscles that induce muscle contraction, so in the absence of acetylcholinesterase, the transmitter acetylcholine will accumulate in nerve tissue. The accumulation of acetylcholine causes repetitive muscle contraction since the muscle continually receives stimulation from the continually firing nerves. (“Sarin Savagery) Delivery of the sarin gas to the subject occurs through inhalation due to its high vapor pressure, yet absorption occurs at a reduced rate by skin contact. An average adult has a lethal dosage of approximately one milligram when inhaled, resulting in the following symptoms responsible for death: paralysis of the nervous system, depression of the respiratory system, and elevated muscarinic secretions. When inhaled, sarin produces hypersecretion of mucus, bronchospasm, and respiratory muscle weakness that combined to cause suffocation; convulsions may begin within one minute while death occurs within five minutes. (Dunn) On the molecular level, “nerve agents combine with the hydroxyl group of a serine residue of the enzyme, giving an inactive phosphonylated form of the enzyme” (Toxicological Properties of Nerve Agents). Acetylcholinesterase cannot bind to acetylcholine to trigger an elimination reaction of acetylcholine: (Toxicological Properties of Nerve Agents) (Eady) Inactivated acetylcholinesterase cannot hydrolyze acetylcholine, preventing its breakdown into choline and acetic acid (Eady). Instigation of a cascade of unregulated muscle contractions due to the compromise of acetylcholinesterase leads to death in a human subject.
Cited references: (1) Dunn, Michael A. and Frederick R. Sidell. “Progress in medical defense against nerve agents.” The Journal of the American Medical Association (1989) 262:5, 649(4). (2) Eady, N. “Sarin Nerve Gas.” 12 October 200028. The major component of the essential oil of peppermint is menthol. It has three chirality centers (n) and therefore eight (2^n) stereoisomers. In the most stable diastereomer (shown below- figure 1), all three of the substituents are in equatorial positions, eliminating 1,3 diaxial interactions. This most stable form is also the one preferred as a flavorant in chewing gum (“Menthol”, 2000). Menthol is also a monoterpene, a cyclic hydrocarbon (“Terpene”, 2000). A terpene is synthesized by the condensation of two isoprene units in a head-to-tail linkage (see below- figure 2), each consisting of five carbons. Thus, menthol, a monoterpene, is a C hydrocarbon. The article I read focused on a study using headspace solid-phase microextraction in addition to gas chromotography/ mass spectroscopy (SPME-GC/MS) to “determine semiquantitative differences in essential oil quality between flowers and leaves of various positions of Mentha x piperita L.” (Rohloff, 1999). The study also compared its results with more complex methods such as steam distillation extraction. Some factors that influence the content and composition of peppermint essential oil are harvest date, plant age, light regime, fertilization, and planting time. Additionally, this study confirmed that older plant parts have higher levels of menthol than younger plant parts do. For example, the percentage of menthol in “leaf 8-9” of a tested Mentha x piperita plant was 24%, while the percentage in the flower of that same plant was only 8%. These figures illustrate that there is about three times more menthol in the older plant parts. It also led to a conclusion that “peppermint plants should be harvested at a growth stage with a relatively high number of basal leaves to obtain an essential oil quality with a high concentration of menthol and a low content of menthone” (Rohloff, 1999). They also concluded that SPME-GC/MS analysis on peppermint essential oil volatiles yielded reliable, confirming results that are less time-consuming than conventional distillation and extraction method. Figures
Cited references: (1) Rohloff, Jens "Monoterpene Composition of Essential Oil from Peppermint (Mentha x piperita L.) with Regard to Leaf position Using Solid- Phase Microextraction and Gas Chromatography/ Mass Spectroscopy Analysis. Journal of Agricultural Food Chemistry." 1999, 47, 3782-3786. (2) www. AccessScience.com. Chemistry: Organic Chemistry. “Menthol”; www. AccessScience. Biology. “Plant Metabolism”; www. AccessScience. Chemistry: Organic Chemistry. “Terpene.” by Melissa deWolfe, 03'29. There are two things that an adhesive must do. The first is that they must make intimate contact at the molecular level with the substrate; the second is that it must then harden to a cohesive solid. Solvent-based adhesives, examples of which are available to the public, are solutions of a co-polymer of acrylonitrile and butadiene. One of the theories that has been suggested to explain adhesion, the electrostatic theory of adhesion, suggests that when two metals are placed in contact, electrons will be transferred between their Fermi levels, and an electrical double layer will be produced. This will give rise to electrostatic forces of attraction across the interface and result in adhesion of the two metals. Another theory, the adhesion diffusion theory advocated by S. Voyutskii, states that when two polymers are placed in contact, interdiffusion of molecules will occur so that the interface will be eventually removed. Technically, this is a form of adhesion. But, the two theories above have very limited scope and cannot be applied to explain various other forms of adhesion. Two other related theories, which attempt to explain adhesion, are the chemical bond theory and the physical adsorption theory. The chemical bonding theory states that chemical bonds can be formed across interfaces. Bonds of all kinds are possible and their strengths are roughly in the order ionic interactions > covalent bonds > Lewis acid and base interactions > hydrogen bonds; the first two types are the strongest and lead to much better adhesion compared to the adhesive forces resulting from the latter interactions. The physical adsorption theory states that Van der Waals forces, which occur between all atoms and molecules when they are close together, exist across interfaces and although they are the weakest of all intermolecular forces, their abundance and collective strength are more than adequate to account for the strengths of adhesive joints. Adhesion phenomenon cannot solely be explained by either one of the four theories suggested above. Rather, all or most of them must be taken into consideration, when trying to explain adhesion theory.
Cited references: (1) by Nihand Rahman, 04'30. Aspirin (acetylsalicylic acid) can exist either in ionic form, or as a non-polar molecule. In its ionic form, it is highly soluble in water. In neutral solution, the ionized form of aspirin is insoluble in fat, and therefore does not pass through the mucosal barrier of the lining of the stomach. However, because the pKa of the carboxyl group on aspirin is 3.5 (moderately acidic), when aspirin is dissolved in a solution whose pH is below 3.5, it remains undissociated (it actually picks up a proton from dissociated HCl in the stomach) and is fat soluble. In this form, aspirin can easily pass through the lipid layer of the mucosal lining of the stomach, causing a steep concentration gradient for diffusion of aspirin through the mucosal barrier into the epithelium (stomach lining). This gradient can be reduced only by removal of the aspirin from the epithelium by blood and cell buffers. This process causes bleeding, which in the average person causes approximately 0.5 to 2.0 ml of blood to drain into the stomach. This causes a trivial amount of damage, but some individuals may lose hundreds of milliliters of blood, or develop anemia (in the case of frequent users of aspirin). And that is why aspirin makes my belly hurt. Structure of aspirin:
Cited references: (1) Davenport, H. W. "Why the stomach does not digest itself." Sci. Am. (January 1972) 226 (1), 86-93. (2) Davenport, H. W. "Salicylate damage to the gastric mucosal barrier." N. Engl. J. Med. (1967) 276 (23), 1307-1312. (3) Hobey, W. D. "Stomach upset caused by aspirin." J. Chem. Educ. (1973) 50 (3), 212-213. by Paula Max-Sohmen, 03'31. Unlike the ink in dry-erase markers, the ink in permanent markers contains only pigments and colorants resistant to light and chemical attack. No article disclosed, however, the specific substances present in dry-erase pigments vis-a-vis the substances present in permanent ink pigments. Furthermore, other web sites provided complementary hypotheses. One web site implied that the formula for white board cleaner is responsible for the erasability of dry erase markers. The water, isopropanol and 2-butoxyethanol in the cleaner eliminates the methyl isobutyl ketone, n-butyl acetate and various pigments and dyes in the dry eraser marks on the whiteboard. Still another web sight suggested that the composition of the whiteboard causes the dry-erase markers to erase. The melamine saturated overlay in The WilsonMart Marker Board Laminate renders dry-erase markers impermanent.
Cited references: (1) J. Chem. Educ. (1980), 57 (4), 270-271. (2) www.scu.edu/SCU/Departments/EnvironmentalStudies/indoor.htm (October 19, 2000); www.ovisonline.com/wa_qa.htm (October 20, 2000) by Peter Law, 03'32. The most common ingredient in non-acetone fingernail polish removers is ethyl acetate, chemical formula C4H8O2. This report on the safety of ethyl acetate and butyl acetate in cosmetics combines the results of 69 journals, experiments, and tests on the substances, so that almost every possible effect of the substances were examined. The report concluded that ethyl acetate was safe for human use, after testing the product for biochemical effects, cytotoxicity, physiological effects, rate of metabolism, and numerous other effects on humans and animals. Its mutative effects, carcinogenic properties, and effects on the reproductive system were also tested. Although it did cause some toxicity and irritation in animals, especially because the scientists got very creative with the tests they performed, ethyl acetate didn’t seem to have any real negative effects on humans. One test on humans found that ethyl acetate was quickly metabolized and hydrolyzed by the human body when inhaled. One of ethyl acetate’s more interesting effects on the human body is that it speeds up the transportation of Na+ and glucose because it can penetrate cells easily. In large doses ethyl acetate had some effects on cellular or DNA functions, but that was only in the animal tests. Ethyl acetate also apparently mutated some cells under certain conditions, but the reports didn’t seem to think that was anything to be concerned about. In fact, the journals didn’t seem to be worried about any of the negative effects seen in lab animals, so they must not have been as dire as the journals made them sound. Ethyl acetate nail polish remover actually seemed very safe when tested on humans, because it didn’t cause any reaction after four weeks of continuous use and application to sensitive skin. Overall, the report concluded that ethyl acetate was safe for humans to use in the normal amounts in cosmetics. Structure of ethyl acetate:
Cited references: (1) TOY, N.J. (EDITOR). Final report on the safety assessment of ethyl acetate and butyl acetate. Washington, DC, USA. J. Am. Coll. Toxicol. (1989), 8(4), 681-705. by Robin Dean, 03'33. According to a case study done by R. Walker, there are no “toxicological concerns…associated with its use as a food additive in accordance with good manufacturing practice” (Walker 1). There may, however, be concerns if MSG is consumed in mass quantities, above levels that are commonly associated with food ingestion. Scientists found that in repeated testing of humans, dogs, mice, rats, and other test organisms, no serious toxic effects were observed. The article postulates that any real concern about the toxicity of MSG surrounds two questions: Is neural damage associated with high intakes of MSG (especially in young animals) and are the symptoms of “Chinese Restaurant Syndrome” actually legitimate results of MSG consumption (typically found in a variety of ethnic foods)? Concerning neural damage, scientists found that the rate of metabolism of MSG and its derivatives is much lower than other amino acids, and thus MSG remains in the animal system for extended periods of time. Through experiments, however, scientists have determined that the toxic nature of MSG relies on its peak level in the blood rather than how long it is present in the system. Thus, there are no toxicological concerns for MSG as a food additive, because peak levels that would be toxic cannot be achieved through food consumption. Furthermore, researchers found that infants can most likely metabolize MSG at the same rate as adults; however, it was reiterated that children under the age of 12 weeks should not contain food additives of any sort. The only way neural damage and toxicity become a factor is when large quantities of MSG are present at the hypothalamus, which ultimately leads to neuronal apoptosis, a scenario which is nearly impossible to create through food consumption. With regards to “Chinese Restaurant Syndrome”, it was found through “double-blind crossover” studies that there is no identifiable relationship between MSG and the symptoms of flushing, chest pain, headache, and drowsiness often associated with the consumption of ethnic foods. (Information obtained from main reference cited below). Structure: MSG
Cited references: (1) Regul Toxicol Pharmacol 1999 Oct; 30 (2 Pt 2): S119-21. (2) Raiten, Daniel J; Talbot, John M; Fisher, Kenneth D. Journal of Nutrition. (1995), 125(11), 2892S-2906S. (3) Manning, Paul D.V. “Monosodium Glutamate.” www.AccessScience.com. by Sam Edmonson, 03'34. When Fleming, Florey, and Chain developed penicillin into a clinical drug in the 1940’s, it was haled as the wonder drug. However, not many people knew the structure and the mechanism behind its clinical success. Penicillin contains a beta-lactam ring attached to a thiazolidine ring (Fig. 1). It blocks an enzyme which cross-link peptidoglycan strands during the bacterial cell wall formation, rendering the cell unable to maintain its shape and unable to contain its cycloplasm contents. In the absence of penicillin, the enzyme called tranpeptidase, which is targeted by penicillin, covalently modifies a serine residue in the site where peptide cross-linking takes place. In the presence of penicillin, this modification reaction causes penicillin to enter the site of this activity (active site ). Upon entering, the proton on the hydroxyl group (Fig. 2) of the serine residue get rip of by the nitrogen on the beta-lactam ring. Also, the oxygen on the hydroxyl group breaks of to form a new bond with the carbonyl carbon at position 7 on the beta-lactam ring. The breaking and the formation of these new bonds form a stable structure that inactivates tranpeptidase enzyme. Due to the inactivity of tranpeptidase, the peptidoglycan layer of the cell wall cannot be syntheses, which leads to a cellular explosion. Recently there has been increased number of bacteria, which carry resistance against penicillin. Some of these bacterial carry genes that transcribe enzymes that can cleave the beta-lactan ring the penicillin molecule useless. This posses a huge risk to our health and without the search by organic chemist and other scientist to discover and synthesize new compound, we will succumb to these microbe.
Cited references: (1) Bio200a Laboratory Manual, Experimental Approaches: The Biology of the Antibiotic Resistance, J Punt and K Heston, Fall 200 edition. (2) Fig.2 Lehninger Principles of Biochemistry 3rd edition, D, L Nelson and M, M Cox. (3) Process May Help Scientists Find New Antibacterial Drugs. Johns Hopkins University News http://www.jhu.edu/news_info/news/home00/aug00/antibiot.html. (4) Fig. 1 University of Oklahoma Health sciences Center Web site http://w3.ouhsc.edu/mi/faculty/tweten/lecture%20pages/mmi/disinfectantimicrobics/DA_29.JPG Access on November 4th, 2000. (5) Lectka, T et al."Catalytic, Asymmetric Synthesis of Beta-Lactams" J. Am. Chem. Soc. 2000, 122, 7831-7832. by Shawn Alexander, 03'35. Rosefuran (C10H14O), a major constituent in rose oil, is responsible for the pleasant fragrance of roses. Buchi first synthesized rosefuran in 1968. Since then, there have been 10 published syntheses, all of which involve numerous steps and the overall yield is often low. Trost and Flygare are currently purposing a new method of synthesis that involves only two steps. This synthesis takes advantage of a recently discovered ruthenium-catalyst. The first step is a simple addition of acetylenes and allyl alcohols in the presence of a ruthenium catalyst, which yields a b,g-unsaturated ketone. In the second step, hydroxylation of the ketone takes place in the presence of catalytic osmium tetraoxide and cyclization occurs with addition of acid catalyst, thereby giving rise to a furan. In this step all the reagents are used up, with water as the only byproduct. It is important to note that there are two limitations to this synthesis. First, if the R group of the acetylene contains a hydroxyl group that favors an intramolecular addition that produces a stable alkoxyalkylidene complex, then such substrate will fail to participate in the reaction. Second, an osmium-catalyzed process will not allow any C-C unsaturation that is more nucleophilic than b,g-double bond of these substrates. Following this protocol, rosefuran can be synthesized from inexpensive and readily available starting materials such as propargyl bromide, acetone and 1-buten-3-ol; resulting in a 23% overall yield of rosefuran. structure of rosefuran:
Cited references: (1) Trost, Barry M; Flygare, John A. "A Practical Synthesis of Rosefuran. Furans from Acetylenes and Allyl Alcohols." J.Org. Chem. (1994) 59, 1078-1082. by Sherry Yang, 03'36. One of my favorite fruits to eat is an apple, in particular the Granny Smith apple. The problem is that I am never able to finish a whole at apple all at once, but whenever I come back to finish my apple, it has turned a disgusting shade of brown. This problem stimulated me to ask why apples turn brown when you leave them sitting out in the open after you have started eating it? The discoloration of apples to a brown color is known as enzymatic browning. Browning occurs when apples are cut or sliced and then exposed to the air. The cutting and slicing of apples has two effects. It brings substrates and enzymes together and also causes damage to the cells and its tissues . This damage initiates the oxidation of the enzyme polyphenol oxidase on phenolic substrates, which causes the browning to occur. The amount of browning correlates with the levels of phenolic compounds present and the nature of these compounds rather than the amount of enzyme activity . The color of the discoloration is determined by the substrates present. In apples, the parts near the core turn brown the most densely. Reducing the oxygen concentration will help to slowdown the browning. In the article, the investigators discovered that the most reactive polyphenols in apples are catechins and both chlorogenic and caffeic acids. However, in different fruits that enzymatic browning occurs, polyphenol oxidase’s oxidize substrates and different rates. For example, PPO prefers to oxidize catechins whereas in pears in pears, PPO prefers to oxidize a different substrate. Control of browning can be achieved by inhibiting PPO activity by heat treatments, addition of antioxidants, and use of inhibitors of PPO such as sulphur dioxide. Substrates: Catechin Caffeic acid Cholorogenic acid
Cited references: (1) O' Beirne, David. "Control of Enzymatic Browning Without the Use of Sulphites." 20.01.99.37. The characteristic orange smell is given by a type of organic molecule called ethyl 3-hydroxyhexanoate. This particular type of molecule is classified as an ester, meaning that one carbon withing the molecule is double bonded to two oxygen atoms. One of these oxygen atoms is bonded twice to the carbon atom, the other oxygen is bonded to both the carbon with the double bonded oxygen and a second carbon chain. In ethyl 3- hydroxyhexanoate, the ester group falls between two carbon chains, one of which is six carbons long and has an alcohol group substituted on the third carbon, the other of which contains only two carbons. Ester molecules are also responsible for the odor of many common foods, including wintergreen, apple, pineapple, strawberry, and rum. structure
Cited references: (1) Distribution of aqueous aroma components in the orange. Moshonas, Manuel G.; Lund, Eric D.; Berry, Robert E.; Veldhuis, Matthew K. J. Agr. Food Chem. (1972), 20(3), 688-90. by Stephanie Kukora, 04'38. It was shown that nitrifying bacteria can not only remove ammonia, they can also remove organic pollutants. This was specifically applied to certain organic chemicals (phenols, mono- and dichlorophenols) that have contaminated drinking water supplies and lead to an unpleasant taste or smell in the water. Phenol is a common pollutant that is easily chlorinated, and it gives water a medicinal taste. The study found that the nitrifying bacteria could remove up to 91% of phenol, 85% of o-chlorophenol, 30% of 2,4-dichlorophenol, and 28% of 2,6-dichlorophenol. These were removed almost immediately after being introduced to the bacteria. They could also remove up to 75% of chlorobenzene, 83% of 1,2-dichlorobenzene, and 79% of 1,4-dichlorobenzene. The chlorobenzene was removed 12 to 14 hours after being introduced to the system, and the dichlorobenzenes were removed 24-28 hours after being introduced to the system. All these chemicals were absorbed most effectively when introduced in very small concentrations, ranging from 1-2 µg/L with varying substrates (ammonia, ammonia and acetate, or acetate). The biological filter of nitrifying bacteria could not remove trichlorophenols that were introduced to them. The authors made an interesting point in their discussion that the enzymatic pathway that degraded phenol could also have the ability to use chlorophenols as well. This would explain the quick uptake of these molecules and their conversion to CO2 (this was found out experimentally by tracing 14C that was introduced in the phenols and benzenes in the CO2 produced by the bacteria). The lag time before the chlorobenzenes were converted was attributed to the gene expression time of an enzyme that could convert chlorobenzenes already coded for in the bacteria’s DNA. Although the experiment did not suggest why the bacteria had the ability to degrade these organic molecules, it did show that this could be applied to removing pollutants in drinking water with copious quantities of bacteria available from sewage treatment plants using biological filters. structure
Cited references: (1) Manem, Jacques A.; Rittmann, Bruce E. J-Am. Water Works Association. 1992, 84(4), 152-7. by Steven Van Name, 03'39. Solvent-borne nail polishes are nail polishes that have a high concentration of organic solvents. Like many organic solvents they are very volatile and if they are unsealed they will evaporate and change the composition of a bottle of nail polish. These organic solvents are actually intended to evaporate in order to give nail polish such qualities as ‘quick-drying’. If there is increasingly less organic solvent and the same amount of solute (in the form of other additives), then the solute will eventually fall out of solution because it is too concentrated. Even though these solvent-borne nail polishes lead to such problems as insolubility of solutes, they are more efficient than their water-based counter parts. Water-based products have a dispersion of particles in aqueous solution, but since they have a low volatile content, the nail polish does not evaporate as well after application.
Cited references: (1) Website- www.dol.net/frank.logullo/femmi.html. (2) Schlossman, Mithcell. “Additives for Water-Based Nail Polish”. J. Cosmet. Sci. (1999) 50 (2), 105-109. by Tamia Harris, 03'40. Erectile dysfunction is the inability to hold an erection long enough for sexual activity. This is caused by certain conditions that affect the blood vessels which restrict blood flow to the penis. A normal penis erection occurs by the relaxing and widening of arteries in the penis that allow an increased blood flow to the two corpora cavernosa, which makes up most of the penis. After the penis is erected, small cavernosal veins contract to restrict the blood flow, thus maintaining the erection. The changes in blood flow are controlled by the release of nitric oxide from cavernous nerves and endothelial cells. The nitric oxide stimulates the output of cyclic guanosine monophosphate (cGMP), which relaxes the smooth muscle cells of the corpora cavernosa allowing the increased blood flow. Sildenafil citrate (Viagra) selectively inhibits the breakdown of cGMP by a specific cGMP phosphodiesterase. Therefore sidenfil citrate works only when the man is sexually aroused (production of cGMP).
Cited references: (1) by Thomas Ta, 03'41. Fireflies use molecular oxygen in order to produce an organic substance, a luciferin (light bearing molecule), which is in an electronically excited state. This is what results in the emission of light. In Fireflies, the luciferin is a benzthiozole. The benzthiozole for the common American firefly is D-2-(6-hydroxy-2-benzothiazolyl) -delta²- thiazoline-4-carboxylic acid.
Cited references: (1) by Tom McNicholas, 04'42. Urine smells after eating asparagus because of sulfur containing compounds (which can also found in the skunk effluvium) that are formed when asparagus is broken down in metabolism. It is evident that this smell is the result of an autosomal dominant gene that only certain people carry, but there is still much debate as to whether this gene affects the production of the sulfur-containing products or alters a person’s sense of smell. There is also some debate as to what the exact products of urine are, but the most conclusive evidence was discovered by Robert White. White rejected the traditional theory that the smell is caused by methanethiol and experimentally proved that the odor produced by urine was a result of other products. By using methylene chloride, he isolated the sulfur compounds in urine. White then used gas chromatography-mass spectrometry to identify the extracted products. He concluded from the analysis that urine contained both S-methyl thioacrylate and S-methyl 3-(methylthio)thiopropionate. In addition, small amounts of several other sulfur compounds were occasionally detected in certain samples.
Cited references: (1) White, Robert H, “Occurrence of S-Methyl Thioesters in Urines of Humans After They Have Eaten Asparagus,” Science 189 (1975): 810-811. by Topher Dawe, 03'43. Salicylic acid fits under the general category of “keratolytics,” or chemical peeling agents. Used over the long term, salicylic acid has a comedolytic effect: It helps decrease the number of clogged pores in human skin (1). To reach this effect, salicylic acid both desquamates and exfoliates: it facilitates the removal of already-dead skin and it enhances the activities of salicylates on the skin which promote the regeneration of skin cells (2). As new skin cells regenerate, old skin is shed and a constant exchange between old skin and a new layer takes place, with the hopeful effect of keeping the skin clean and youthful in appearance (3). In order to accomplish this, salicylic acid is included in many face washes, including three that I frequently use: biore Anti-Acne Cleanser, biore Warming Deep Pore Mask, and Neutrogena Deep Clean. The cleansers use an alcohol as a “carrier for the acne treatment ingredient”--salicylic acid. Based on information from the biore Company, detailing that their cleanser has a pH ranging from 6.0-7.0, it can be imagined that most face washes containing salicylic acid would fall somewhere between these boundaries. The mask actually has a pH of 8.0-9.0, but it is used basically to open the pores rather than clean and exfoliate the skin. Upon contact, the acid gently eats away at both the outer epidermis and the pore-clogging bacteria and dirt, to facilitate a cleaner, healthier complexion (4,5). Chemical peeling is actually something that can be done by dermatologists on a much larger scale; using a more concentrated acid, they can complete a skin peel within ten minutes that reaches much deeper into the skin layer and requires a period of healing. In this procedure, chemical solutions like glycolic acid, trichloroacetic acid, salicylic acid, lactic acid, and phenol can be used; each application produces “ separation and eventual peeling of layers of skin,” just like the face washes I use (6). To get an idea of the doses of acid my skin is receiving daily, I compared each of the products that I may choose to use throughout the day. Several of the other face washes I own actually did not contain salicylic acid itself, but another form of keratolytic. In the three products I mentioned before (the two biore and one Neutrogena products) the bottles did not report the percentage of salicylic acid, but I believe the amount is generally around 0.5%-1% acidity (the Neutrogena bottle formerly had the exact percentage included in the ingredients and that is the number that I remember from having read it before). My Neutrogena Clear Pore Treatment is 2% salicylic acid, slightly stronger because it is the more potent, overnight keratolytic. I also have a tube of Clinique Concealing Cream that contains 1% salicylic acid as its “active ingredient.” In comparison, wart remover, necessarily the most potent (as it is removing a large section of tissue rather than one skin layer at a time) is 17% salicylic acid. Small wonder that my face medicines come in such diminished potencies. [As a side note, I would like to mention that my dermatologist has also prescribed a 4% benzoyl peroxide solution and a.1% adapalene solution for my skin care—it is amazing that my body has not rebelled!] Interestingly enough, although salicylic acid is, on the whole, something that leads to better health—clearing up acne and removing unwanted warts—it can have nasty side effects. If used in too great a quantity, salicylic acid poisoning actually can develop, leading to confusion, dizziness, headaches, rapid breathing, ringing/buzzing in ears, and (as a general rule in all salicylic acid use) moderate to extreme skin irritation (1). Salicylic Acid7:
Cited references: (1) http://www.nlm.nih.gov/medlineplus/druginfo/salicylicacidtopical202516.html (2) Abstract for Japanese patent: Application: JP 99-229474. (3) Abstract for Czechoslovakian article: “Effective and safe pharmacotherapy of acne vulgaris and the treatment of solar damage of the skin.” Fendrich, Zdenek, et al. Ceska Slov. Farm: 2000. pp 62-67. (4) biore Fact Sheet, sent by the company at my request. (5) biore Ingredient Identification and Function Sheet, sent by the company at my request. (6) http://www.asds-net.org/chempeel.html (7) Lawson, Emma E., et al. “Interaction of salicylic acid with verrucae assessed by FT-raman spectroscopy.” JOURNAL (1998), 343-351. by Caitlin Kight, 03'44. Halothane, 2-bromo-2-chloro-1,1,1,-trifluoroethane (CF3CHBrCl), is a chemical used as an inhaled anesthetic agent. The staggered conformation of Halothane has the following bond lengths: C2-H = 1.106 Å, C1-F1 = 1.370 Å, C1-F2 = 1.377 Å, C1-F3 = 1.378 Å, C2-Cl= 1.791 Å, C2-Br = 1.915 Å, C1-C2 = 1.524 Å. The eclipsed conformation has these bond lengths: C2-H = 1.106 Å, C1-F1 = 1.370 Å, C1-F2 = 1.370 Å, C1-F3 = 1.381 Å, C2-Cl= 1.800 Å, C2-Br = 1.913 Å, C1-C2 = 1.561 Å. In the staggered conformation, or the minimal energy conformation, Halothane achieves the following bond angles in degrees, all of which deviate from the ideal tetrahedral bond angle: F1-C1-F2 = 107.6, F1-C1-F3 = 107.8, F2-C1-F3 = 106.8, F1-C1-C2 = 113.0, F2-C1-C2 = 110.5, F3-C1-C2 = 110.8, C1-C2-H = 109.8, C1-C2-Cl = 109.7, C1-C2-Br = 109.3, H-C2-Cl = 108.6, H-C2-Br = 107.4, Cl-C2-Br = 112.0. The Cl-C2-Br angle is slightly larger than the tetrahedral bond angle, 109.5, because of the large Van der Waal radius of bromine. The F1-C1-C2 angle is larger than the tetrahedral angle because of the smaller angles in the F-C-F bonds. The energy difference between staggered and eclipsed conformations is 5.0 kcal/mol. The dipole moment for a molecule of halothane in the gas phase =2.0 D. (1) Halothane is used as an anesthetic because it depresses the central nervous system in humans. It is a clear, nonflammable, highly volatile liquid. When halothane is used as an anesthetic, it often causes amnesia, analgesia, anesthesia, and respiratory depression. Some patients experience "halothane hepatitis", which may include fever, anorexia, nausea, vomiting, and may advance to cause death. (2)
Cited references: (1) Scharf, D.; Laasonen K. "Structure, effective pair potential and properties of halothane." Chem. Phys. Lett. (1996), 258(1,2), 276-282. (2) Occupational Safety and Health guideline for halothane. OSHA website. (Accessed 11/2000). by Andrew Hollander, 03'45. The main ingredient in white onions that triggers tears has been found to be a sulfur-containing compound. A Finnish scientist, by the name Artturi Virtanen did the first research in 1961. He discovered that onions contain trans-(+)-S-(1-propenyl)-L-cysteine sulfoxide, which is a positional isomer of alliin. This chemical compound, referred to as the lacrimatory precursor or LP, is converted by the allinase enzyme into the lacrimatory factor or LF. It is this substance that causes people to cry when they are cutting up onions. Eric Block has also contributed to the identification of these unique sulfur compounds found in onions. He calls the compound that causes people to tear up, (Z)-propanethial S-oxide. This compound forms when the onion’s skin gets damaged or upon slicing. The act of cutting the onion sets the allinase enzyme into action and thus catalyzes a series of spontaneous reactions that convert the lacrimatory precursor into the lacrimatory factor.
Cited references: (1) Science News (1990) 137, 380. (2) Scientific American (1985) 252, 114-119. by Marie-Elena Davis, 03'46. There are many aspects of Aloe Vera that make it such a good product for burn relief. Pretty much all of aloe (99%) is water, which does help (although minimally) in relieving the pain associated with a burn (2). However, the other components in the 1% do a lot to help alleviate burns. In the plant’s sap, there are these phenolic compounds called anthraquinones (2). Two in particular, aloin (also known as barbaloin) and emodin, are aspirin-like compounds that act as pain relievers (1). Also, aloe contains a high magnesium content, which makes it capable of relieving pain (1). These pain-relieving chemicals are absorbed into the epidermal cells and numb them, making the burn less painful (1). Also, there are polysaccharides that act as moisturizers (2). These polysaccharides are also absorbed by the skin, hydrating it and also absorbing a lot of the heat that emanates from a burn (2). That’s the main problem of a burn, the excess heat that has been absorbed by the skin cells. The polysaccharides, in addition to the water, soak up this heat, reducing a lot of the redness and pain. But there is another active ingredient in aloe that acts an anti-inflammatory, bradykinase (2). This enzyme, when applied topically, is absorbed by the skin cells and helps reduce redness and irritation that is caused by burns (2). Now, in the case that peeling might occur, one can apply aloe to the flaking skin, and aloe’s cohesive effect will fasten together any flaking/ peeling skin, yielding smoother skin (2). Something else one must worry about when burned is ischemia, when blood flow is restricted to cells (in this case skin cells) as a result of a burn. Again, aloe can help. It’s biochemical configuration helps block prostanoids, the chemical that causes ischemia from forming (1). And finally, with all the immediate effects of the burn lessened, the abundance of fatty acids in Aloe helps the damaged cells heal and mature (1). Wow, what an amazing product!
Cited references: (1) Robson, M.; Heggers, J.; Hagstron, W. "Myth, Magic, Witchcraft, or Fact? Aloe Vera Revisited" J. Burn Care Rehabil. (1982) 3, 157-163. (2) http://www.positivehealth.com/permit/Articles/Aloe%20Vera/atherton.htm by Matthew Schechter, 04'47. The reaction of an oxalate ester with hydrogen peroxide along with fluorescent dye produces chemical light. These active ingredients and the reaction processes between them allow glow sticks to “glow.” This result is called chemiluminescence, or chemical light; it is the production of light from a non-heat generating chemical reaction. Generally, to glow in the dark a substance needs to have stored energy and a chemical that will use the energy to create light. The glowing effect that occurs is due to an excess of energy. This energy comes from a movement of electrons. When one of these reactions occurs electrons are excited and move energy fields, the electrons then eventually return to the original field. Once the electrons are returned there is an excess of energy from the transformation. This excess of energy is stored and waiting to be used. This stored energy is either rapidly or slowly depleted causing a light to be given off. Once the limiting reactant is depleted, the reaction no longer occurs, thus ending the glowing effect. Specifically in glow sticks, to keep the reaction from occurring prematurely, the compounds are kept separate by storing one in a very thin capsule, which is broken by flexing or bending the product tube. The thin capsule contains dilute hydrogen peroxide in a phthalate ester solvent. When mixed with the surrounding solution of phenyl oxalate ester and a fluorescent dye (such as 9,10-bis-(phenylethynyl)anthracene for green), the hydrogen peroxide oxidizes the phenyl oxalate ester, with the help of a salicylate catalyst, to a peroxyacid ester and phenol. The peroxyacid ester is, thus, unstable and gives off energy to the dye as it decomposes to form more phenol, and most important, a highly energetic stable intermediate, presumed to be a four-membered ring dimer of CO2. As the cyclic dimer decomposes into two CO2 molecules, it gives up its energy to a waiting dye molecule, which then fluoresces. The stoichiometry of the reaction is represented as: Fluorophor ArO-C-C-OAr + H O à 2ArOH + 2CO (1) (catalyst) where Ar is an electronegative aryl group. Although most chemiluminescence reactions involve emission from a reaction intermiediate derived from one of the reagents, the peroxyoxalate reaction transfers energy to fluorescent molecules, which then in turn emit light during relaxation from the first singlet excited state. The reaction method outlined is:, oxalate ester + H O --> intermediate (I) + products (2) I + fluorophor (F) --> F* + products (3) F* --> F + hv (4) Or a working partial mechanism for (1) can be detailed as follows: ArO-C-C-O-OAr + H O --> ArO-C-C-O-OH +ArOH ArO-C-C-O-OH --> +ArOH + Dye --> Dye* + 2CO Dye* -->Light The first substitution that occurs is of H O for a phenol (ArOH). H O is acting as the nucleophile as the phenolates acts as leaving groups. This reaction is rate limiting, therefore, the rate of reaction (2) determines how long chemiluminescence will last. The reaction of an oxalate ester with hydrogen peroxide produces at least one, but possibly two or more, highly energetic intermediates capable of generating the excited singlet state of fluorescent molecules. Radioactive decay of the singlet-excited fluorescent molecule produces the observed light emission, and a variety of fluorophors may be used to produce a range of colors. How does temperature affect the rate of reaction? Reaction rates generally increase with temperature. There are two reasons why the reaction rate goes up with temperature: 1. As temperatures go up, molecules move more quickly on average, so there are more collisions (and the molecules must collide to react), 2. It takes a certain threshold energy (called the activation energy) for the colliding molecules to react. At higher temperatures, a larger fraction of molecules are at or above the threshold energy, so the reaction goes faster. A higher temperature will make the reaction go faster, so the sticks will glow more brightly, but they will not last as long.
Cited references: (1) J. Chem. Educ. (1974) 51(8), 528-529. (2) (http://www.complast.com/cyalume/cyalume_history.htm (3) (http://www.cyalume.com/classrm.html (4) (http://www.cyalume.com/quesansw.html (5) (http://pubs.acs.org/cen/whatstuff/stuff/7703scit4.html (6) (http://www.chem.leeds.ac.uk/delights/texts/VV_exp_26.htm (7) (http://antoine.frostburg.edu/chem/faq/lightstick.html by Michelle Pham, 03'48. Synthetic dyes (one class of which is Azo dyes that I will be using as an example) undergo photofading when exposed to certain wavelengths of light. When a dye molecule is exposed to light, the absorbed energy must be released somehow. What happens is that an electron from the HOMO (Highest Occupied Molecular Orbital) is promoted to the LUMO (Lowest Unoccupied Molecular Orbital) (Kuramoto). This energy is released through a variety of means, some of which can be phosphorescence, or fluorescence. What often happens though, is that the molecule undergoes some sort of change like a reduction, oxidation, intermolecular rearrangement or other (Kuramoto). For example, as shown below, an azo dye, which has an N=N bond, can undergoa reduction reaction and become two amine molecules.
Cited references: (1) N. Kuramoto "The Photodegredation of Synthetic Colorants" Adv. Color Chem. Ser., 4, 196-253 (1996). (2) D. M. Wiles and D. J. Carlsson "Photodegradation" Access Science, 1-3 (2000). by Romie Gibly, 04'49. Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID). Drugs of this character are COX-1 (cyclooxygenase-1) and COX-2 (cyclooxygenase-2) inhibitors. COX-1, in particular, is “expressed at a fairly constant level in cells, including the gastrointestinal mucosa and platelets” (Feldman and McMahon). COX-1 is an essential substance to the body because prostaglandins, such as E2 (PGE2), are created by COX-1 in the gastrointestinal mucosa and are necessary for “protecting the gastrointestinal epithelial lining against ulceration” (Feldman and McMahon). Inhibition of COX-1 also decreases the “production of platelet thromboxane A2, predisposing patients to bleeding” (Feldman and McMahon). Overall, the inhibition of COX-1 and COX-2 in “traditional NSAIDs” leads to more ulcers, intestinal bleeding, GI track complications, and more stomach pain in general than just pure COX-2 inhibitors. Acetaminophen on the other hand “does not inhibit platelet aggregation or induce GI ulceration” (Hersh, Moore, Ross). “It is ~10 times less potent than aspirin as a peripheral COX inhibitor, yet has almost equivalent potency to aspirin in blocking COX in the brain.” Ibuprofen structurally is closer to aspirin and therefore has similar COX-1 and COX-2 inhibitor effects as aspirin.
Cited references: (1) Hersh, Elliot V.; Moore, Paul A.; Ross, Gilbert L. “Over-the-counter analgesics and antipyretics: a critical assessment” Clin. Ther. Vol. 22, Issue 5 (2000) p.500-548. (2) Feldman, Mark; McMahon, Alexander T. “Do cyclooxygenase-2 inhibitors provide benefits similar to those of traditional nonsteroidal anti-inflammatory drugs, with less gastrointestinal toxicity?” Intern. Med. Vol. 132 Issue 2 (2000). p.134-143. by Adam Foye, 04'50. Nanotubes are a form of carbon that was discovered in the late 1980's. To understand the importance of nanotubes, you must understand their structure and the properties that arise from this structure. The structure is amazingly simple, as a nanotube is comprised of repeating unit, which consists of a hexagonal ring of carbons. A nanotube is merely a sheet of these units rolled up, creating a cylinder. The diameter of this tube is only 2.2 nm. Nanotubes can also be created that are composed of coaxial layers of these cylindrical carbon sheets compacted so that only approximately 0.34 nm separate each successive layer. The tube formation is able to hold together because the bending of the C-C bonds stabilizes the structure so that it is even more stable than graphite. These tubes are incredibly strong because of the stability of the structure. Furthermore, the structure of the nanotubes enables the conduction of an electrical current and the conductivity varies by how the tube is folded. One type of nanotube, called the 'armchair nanotube,' shares the same properties as metal conductors. Another type, called the 'zigzag nanotube,' is an excellent semi-conductor. The strong structure and the excellent conductivity properties are what make the electronics industry so interested in nanotubes. Nanotubes can be used as a replacement for silicon in semi-conducting computer chips or as a replacement for copper wires in electronic circuitry.
Cited references: (1) S. Iijima "Helical microtubules of graphitic carbon" Nature, 354:56-58, 1991. (2) R. Taylor and D. R. M. Walton "The chemistry of fullerenes" Nature, 363:685-693, 1993. (3) Fullerene: http://www.AccessScience.com/server-java/Arknoid/science/AS/Encyclopedia/7/75/Est_757287_printable.html. (4) Nanostructure: http://www.AccessScience.com/server-java/Arknoid/science/AS/ResUpdates/1998/YB_980525_printable.html by Jeff Kearns, 03'